1. Field of the Invention
The present invention relates to a method of preparing a particulate phase toner for use in an electrophotographic image forming apparatus. More particularly, the present invention relates to novel methods of preparing a particulate phase toner by using fractional dissolution, rather than pulverization and chemical preparation to easily control the size and a shape of toner particles. The present invention improves fluidity of the toner, eliminates the environmental pollution of the prior methods for producing the toner. The invention is also directed to the particulate phase toner prepared by the methods of the invention.
2. Description of the Related Art
The toners that are conventionally used in electrophotographic image forming apparatus include a pulverized toner prepared by pulverization or a chemically prepared toner prepared by chemical processes.
The pulverization method is a classic method for preparing a toner. This method produces a mixture by uniformly melting and dispersing a colorant, a charge controlling agent (CCA), a releasing agent, etc. in a binder resin. The mixture is pulverized to a particle size of between several micrometers and tens of micrometers by a mechanical method such as an air flow type or mechanical pulverizer. The pulverized particles are distributed according to a particle size and external additives are evenly applied to the particles such that the toner has good fluidity, charge stability, cleaning properties, and the like.
However, the method of preparing a toner by pulverization has the following problems: i) it is not easy to control the size of the prepared toner particles; ii) since a shape of the pulverized toner particle cannot be controlled, the toner particles are rough and irregular, thereby increasing the contact surface between adjacent toner particles and reducing fluidity; iii) the size distribution of the toner particle is very broad, and thus, only toner particles having a size within a particular range are fractionated again and used, resulting in a low yield; iv) it is difficult to obtain and control the electric property of the surface of the particles due to their irregular surface; v) weight distribution of the particles is broad, thereby deteriorating transfer and developing properties; and vi) it is not easy to disperse internal additives in the binder resin.
The method of preparing a toner by chemical preparation is a modified version of the method of the pulverization, in which the toner is prepared via a complicated chemical treatment process without using the pulverization. The toners prepared by this method are classified into a chemical toner, a polymerized toner, an in-situ polymerized toner, a suspension polymerized toner, an emulsion polymerized toner, an emulsion aggregation/aggregated toner, a latex aggregation/aggregated toner, a controlled agglomeration toner, a capsule toner, a microcapsule toner, an encapsulated toner, a microencapsulated toner, etc. In this method, toner particles are prepared in a chemical manner and the external process of adding additives is the same as in the pulverization.
However, the method of preparing a toner by the chemical preparation also has the following problems: i) the preparation process is complicated, which increases the price of the toner; ii) in the case of the polymerized toners, unreacted monomers, dimers, or oligomers remain and cause environmental problems, such as a bad smell, and inversely affect the durability of the toner; iii) dispersion stabilizers, surfactants, that are often used in large amounts have a negative influence on a charging property of the toner, it is difficult to remove these materials, and a complicated process is required to remove these materials; and iv) in the case of the suspension polymerized toner, the particles are completely spherical, and thus, the cleaning property of the toner is deteriorated.